dovecot pre-install issue

Wed Nov 16 20:20:31 UTC 2016

> On 16 Nov 2016, at 13:32, soumitri at iitk.ac.in wrote:
> 
> Hi,
> 
> Thanks for the reply. I guess RHEL choose v2.2.10 <http://dovecot.org/list/dovecot-news/2013-December/000268.html> as it is a good release with all the things working.
> 
> My source of confusion are from 
> 1) http://dovecot.org/oldnews.html <http://dovecot.org/oldnews.html>
> I have gone through each release update news. Lots of work and bug fix after v2.2.10 <http://dovecot.org/list/dovecot-news/2013-December/000268.html>, got me confused. 
> E.g. in v2.2.13 has a fix " copied below"
>  <http://dovecot.org/releases/2.2/dovecot-2.2.13.tar.gz>
> director was somewhat broken when there were exactly two directors
> 	  in the ring. It caused errors about "weak users" getting stuck.
> 2) http://wiki2.dovecot.org/Design/DoveadmProtocol/HTTP <http://wiki2.dovecot.org/Design/DoveadmProtocol/HTTP>
> An interesting feature to explore post setup. 
> With thanks & regards,
> Soumitri Mishra
> http://home.iitk.ac.in/~soumitri/ <http://home.iitk.ac.in/~soumitri/>
> On Wednesday 16 November 2016 04:31 PM, Thierry de Montaudry wrote:
>>> On 16 Nov 2016, at 11:06, soumitri at iitk.ac.in <mailto:soumitri at iitk.ac.in> wrote:
>>> 
>>> Hello all,
>>> 
>>> I am going for a dovecot director based setup (2 director+ 2 imap), more imap servers will be added later  depending on demand/load. Presently I have 12000+ dovecot users with Maildir quota varying from 1 GB to 20GB. (peak hour IOPS 50000+)
>>> 
>>> I am having 2 options in choosing dovecot version.
>>> 
>>> 1) Old stable release. I.e RHEL, with prebuilt binary. This will be having less trouble in managing. Why RHEL still using version 2.2.10.
>>> 
>>> 2) Latest release with best features and lesser known bugs. I.e CentOS7 with with latest compiled version. I have to be more involved if a bug is found.
>>> 
>>> I will prefer a less admin work after the setup, with all/most features working.
>>> 
>>> If you have a recent similar setup/dovecot gurus, Pl. suggest.
>>> 
>>> With thanks & regards,
>>> 
>>> -- 
>>> 
>>> Soumitri Mishra
>>> http://home.iitk.ac.in/~soumitri/ <http://home.iitk.ac.in/~soumitri/>
>> Hi,
>> 
>> Running since about 6 month a new setup with 2 directors and 12 IMAP/POP3/LMTP/Sieve servers for mail storage (Maildir), to handle  500K+ users, all straight of CentOS 7 (good old yum and dovecot 2.2.10). It works very well, install is straight forward, event though it needs a bit of optimisation for this kind of traffic. Each user is assigned an IP for the redirection, which dovecot handles very well. And the deployment of new storage machine can be done in less than 30mn.
>> I didn’t have any problem with bugs up to now. But knowing that most access is done via a webmail interface (Roundcube) or POP3, we are not confronted with specific clients and IMAP problems you see now and then.
>> 
>> Hope this help. Regards,
>> 
>> 	Thierry
>> 
>> 
> 

Hi,

I understand your concerns about new versions and bug fixing, but after running this system for more than 3 year, trying to keep up to date all the time… needed a rest. That why we moved to the “out of the box” version, and let’s see. And it works.

About the director. There is 2 ways to use it:

1. you have multiple front end for some NFS or other single storage, it should balance the load between them. I tried it, but EMC, NetApp or other wouldn’t handle the IO/s, and that’s where there must be some limitations in remote FS (mainly on indexing).

2. you spread your users between 2 or more storage machines (that’s what we do, 12 of them currently) that each run dovecot. You can define in you DB the IP where your user’s mail is stored, and the director will redirect whatever protocol (IMAP. POP3, LMPT, Sieve) to the machine where the user belong. When we did the move from NFS to that solution, the load on all the servers were reduce by at least 50 to 60%… if not more. And it allowed us to move from 7 webmail/pop3 front end to 2, and 5 MXs to 2,  using 2.2.10 from CentOS 7.

About the new features… well it does look good. But 2.2.10 still allow you to run remote doveadm commands, so not ready to move yet. Even though I do like it, but so much to do, and so little time to do it...

Regards,